While I am devouring a gorgeous plate of dorado with sautéed “mangetouts,” the glorious name for the peas in their pods that means “eat all,” I complain that French women seem to eat enormous lunches and totter around on heels without ever exercising. Not true, S says. She tells me about the dance studio she goes to in the Opera district, called Elephant Paname. I take a quick note on my phone, then we order the chocolate cake...